An internal investigation at troubled computer giant Dell has revealed that senior management were aware of accounting irregularities which were being used to achieve quarterly financial targets.

As a result of the year-long investigation which concluded this week Dell, the world's second-largest PC maker, will restate its results from the beginning of its 2003 financial year to the first quarter of 2007.

Dell said it expected the total change in net income for the period to be a reduction of between $50-$150 million (€37- €111 million). During that period the company had total net income of about $12 billion.

In a conference call with analysts, Dell's chief financial officer Don Carty said Dell's financial statements for the period should no longer be relied upon.

"The accounting errors and irregularities that will be corrected are significant because of the combination of the number of issues identified, the qualitative nature of many of the issues, and in some cases, the dollar amounts involved," said Mr Carty.

He refused to name the senior executives who had been aware of the practices or what disciplinary action had been taken against them.

Dell said the investigation team, which included forensic accountants KPMG, looked at more than five million documents, interviewed more than 200 staff worldwide, and reviewed thousands of journal entries.

A spokeswoman for Dell Ireland could not say whether any employees at its Irish operations were questioned as part of the investigation and said all communications on the matter were coming from corporate headquarters.

Dell is one of the Republic's largest private sector employers with almost 4,500 staff. Its Limerick site, which manufactures PCs mostly for the European market, employs 3,000. Another 1,500 are employed in Cherrywood, Co Dublin in sales, support and marketing roles.

Mr Carty said a separate investigation by the US Securities and Exchange Commission (SEC) was ongoing and there was no guarantee that this would not reveal further issues.

The Dell investigation found changes to various reserve and accrued liability accounts designed to enhance internal performance and results. It also discovered a number of instances where business units provided incomplete or incorrect information about these activities to internal and external auditors.

Dell now expects to file its restated accounts with the SEC by the first week of November. Mr Carty said a number of changes would be introduced at Dell including providing additional accounting training for staff.